This device relates to a straight edge guidance system for cutting carpet, vinyl, linoleum floor coverings and sheet goods.
When installing carpet at a job site, the installer will usually measure the room, lay out the tack strip, lay out the carpet pad, cut the carpet pad, lay out the carpet, and cut the carpet to fit the size of the room. At some place in the room, the installer will have to make a seam by joining two pieces of carpet together with a melt tape. The melt tape consists of a thick piece of paper having an adhesive and nylon threads deposited on one surface of the tape. The melt tape is centered below the two pieces of carpet such that the adhesive and nylon threads are in contact with the carpet backing. The installer will melt the adhesive on the melt tape with an iron, butt the two carpet edges together and then apply weight, usually the installer's tool box, to the newly formed seam.
The tools most often used by an installer to cut the carpet are a flat straight edge and a utility knife. Several problems may arise during the installation of carpet when using these tools. First, the flat straight edge can move off the line of cut during the cutting process. Second, the weight of the installer can cause the carpet to move away from the installer and off the line of cut. And third, the installer's hand can wobble during the cutting process which, in turn, causes lateral movement in the blade as the blade cuts the carpet. These three problems are all factors which influence whether the carpet has been cut in a straight fashion. It is easier to form the seam when each piece of carpet has a straight cut because the carpet edges will lay flat next to each other. If one carpet edge does not have a straight cut then the seam will be visibly noticeable.
The "double cut" is another problem that occurs when an installer uses a flat straight edge and a utility knife. The "double cut" is an industry term used to describe what happens to carpet as it is cut from the stock roll. After the required amount of carpet is pulled from the stock roll, the installer will lay the flat edge on top of the roll and cut the carpet as it sits on the stock roll with a hand held utility knife. Often the installer will put too much downward pressure on the utility knife causing the blade to cut not only the top layer of carpet but also the carpet located beneath the top layer still on the roll. This piece of cut carpet still on the roll is damaged, and if installed, the carpet yarn over time will start to unravel from the cut area.
A final problem experienced by carpet installers is what is commonly known in the industry as "seam peaking." Whenever two adjoining pieces of carpet are brought together to form a seam, the carpet edges at the seam may "peak" or lift up causing the seam to be visibly noticeable. As the installer joins the two pieces of carpet together, the hot iron is often left unattended on a section of melt tape in front of the installer. This will cause the adhesive on that section of melt tape to overheat. When the adhesive on the melt tape becomes too hot, the adhesive can run and can cause the adhesive to be distributed unevenly. Additionally, the hot adhesive will soften up the carpet backing and the thick paper on which the adhesive is deposited. This will cause the carpet backing and the thick paper to become more flexible. Together, this creates a condition at the seam where some areas of carpet backing are hotter than others, some areas of carpet backing are more flexible than others and some areas of carpet backing have more adhesive than others. As the adhesive cools, any one of these conditions can create stress at the seam which will cause the seam to "peak" or lift up.
Most of these problems resurface again when installing vinyl or linoleum floor coverings. The same tools are used to cut vinyl or linoleum floor coverings, except the installer will usually use a vinyl knife. The vinyl knife has a stronger cutting blade which is required because these floor coverings are rigid and generate a great deal of resistance when they are cut. When installing vinyl or linoleum floor coverings it is critical to have a straight cut in order to form a seam and to match a pattern. The slightest imperfection in the cut will be visibly noticeable when dealing with these floor coverings. These imperfections are caused when the straight edge moves off the line of cut during the cutting process, the weight of the installer causes the floor covering to move away from the installer and off the line of cut or there is lateral movement in the blade during the cutting process.